1. Field of the Invention
The present invention relates to an installation for the continuous rehabilitation of a ballast bed resting on a subgrade for supporting a track including two rails, which comprises an elongated machine frame means extending in a longitudinal direction and supported on the track by undercarriages for movement in an operating direction, the machine frame means having a rear end in the operating direction. Mounted on the machine frame means are a vertically adjustable ballast excavating device for continuously excavating dirty ballast, a screening device for cleaning the excavated dirty ballast, a conveyor device for conveying ballast to a storage bin, and a discharge device arranged to receive bulk material from the storage bin and to discharge the received bulk material to the subgrade.
2. Description of the Prior Art
U.S. Pat. No. 4,892,151 discloses an installation for the rehabilitation of a track ballast bed, which comprises an elongated machine frame supported on the track for movement in an operating direction. Mounted on the machine frame is a vertically adjustable ballast excavating device including an endless excavating chain which continuously receives and removes dirty ballast from the ballast bed. In a direction opposite to the operating direction, the excavated dirty ballast is conveyed to a screening device mounted on a separate machine frame coupled to the first-named machine frame, and the dirty ballast is screened by this device to produce cleaned ballast and detritus. The detritus is conveyed by a conveyor band arrangement forwardly in the operating direction for discharge into freight cars or on the shoulders of the track. The cleaned ballast is conveyed by another conveyor band arrangement to a storage bin on the machine frame and the storage bin has a discharge device for discharging the cleaned ballast on the subgrade by means of discharge conveyor bands which are pivotal in a horizontal plane and, additionally, outlets arranged laterally of the discharge conveyor bands at the tie ends. The installation may be used for a total removal of the ballast so that a totally new ballast bed may be laid, in which case the separate machine frame carrying the screening device is uncoupled and is replaced by freight cars which receive and remove the dirty ballast. With respect of delivering bulk material to an existing ballast bed for the rehabilitation thereof, this installation is limited to the cleaned ballast coming from the screening device.
U.S. Pat. No. 4,913,240 discloses a machine which can be used selectively for cleaning the ballast bed supporting a track and for completely renewing it. This machine comprises a machine frame whose opposite ends are supported on the track by undercarriages and a vertically adjustable excavating device arranged on the machine frame centrally between the undercarriages and including an endless excavating chain for continuously excavating dirty ballast. The dirty ballast is conveyed by a conveyor band to a ballast screening device arranged forwardly of the excavating device in the operating direction for cleaning the dirty ballast. If a total removal of the ballast bed is desired, the dirty ballast is further conveyed without screening to a front end of the machine frame where it is discharged. If the dirty ballast is screened, only the detritus coming the screening device is forwardly conveyed for removal while the cleaned ballast is conveyed by a conveyor device to a discharge device behind the ballast excavating point in the operating direction for redistribution in the ballast bed. Two additional adjacent conveyor devices are arranged at the rear end of the machine frame for receiving additional track bed material from storage cars coupled to the machine frame. One of the additional conveyor devices is arranged to deliver additional track bed material by way of a transfer conveyor band to the discharge device while the other additional conveyor device is connected to discharge chutes leading to the shoulders of the track behind the discharge device. This installation has a relatively complex structure and is difficult to operate because, in addition to the excavation, several discharge points as well as planing, redistributing and compacting devices must be monitored.